Until recently, I'd have said the Tena Slip Maxi (the plastic-backed kind). They fit extremely well, are pretty absorbent, swell nicely, have a smooth, soft plastic exterior, and the tapes are pretty decent. Even the colouring is pretty nice.
Recently, however, I have fallen in love with the Snuggies Waddler Overnight, which is more absorbent, swells more than any other nappy I've ever tried, and has the most authentic "babyish" look of any nappy I have ever tried. Rearz and Comficare are great for the waddle experience, but a bit too thick when dry for my tastes. In my experience, a nappy doesn't really fit comfortably until after the first wetting.